Spark gaps can be used to bleed off overvoltage peaks. A spark gap usually comprises a hollow body of insulating material, which forms a discharge space between two electrodes. If the voltage between the two electrodes increases to an ignition voltage, the electrodes are shorted by a spark. Spark gaps serving as arresters are overvoltage protection devices in which, after ignition, the short-circuit current bleeds off the voltage peak that arises.
However, in the case of DC voltage, the spark and the associated flow of current are not extinguished as soon as the voltage falls back below the overvoltage. This only happens when the voltage decreases to below the arc burning voltage of the spark gap, said arc burning voltage counteracting the applied DC voltage. When the voltage is below the arc burning voltage, the arc is quenched autonomously.
In order to increase the voltage at which the sparks in an overvoltage protection device are extinguished, it is possible to connect a plurality of spark gaps in series so that their arc burning voltages add up. However, the ignition voltage also increases as a result, said ignition voltage being required to ignite all the spark gaps. The ignition voltage at which the spark gaps of a series connection of N spark gaps ignite is approximately N times the ignition voltage of a spark gap multiplied by 0.7. This has the effect that the protection level of such a series connection of spark gaps is appropriately high. The aim, however, is a multiple spark-gap arrester having the lowest possible ignition voltage or the lowest possible ignition value, in the ideal case having the ignition voltage of a single spark gap.
To reduce the ignition value, previous approaches have interconnected each spark gap with a capacitor, for example, so that the increasing pulse voltage is gradually applied to each gap dynamically. Another approach is an auxiliary ignition gap arranged in parallel with the multiple spark gap, said auxiliary ignition gap providing an ignition transformer for each spark gap, for example. German Patent Application DE 102 30 827 A1 discloses triggering a multiple spark-gap arrester by means of a parallel auxiliary ignition gap.